1. Field of the Invention
The invention relates to a ceramic electronic component, a method of manufacturing the same, and a collective component and, more particularly, to a ceramic electronic component in which an external conductor, such as an external terminal electrode, is formed on a principal surface and which is obtained by breaking a collective component along a predetermined break line, a method of manufacturing the same, and a collective component from which a plurality of ceramic electronic components may be obtained by dividing the collective component.
2. Description of the Related Art
A large number of monolithic ceramic electronic components, typically, monolithic ceramic capacitors, are used in electronic apparatuses, such as cellular phones and personal computers. Generally, the monolithic ceramic electronic component includes a rectangular parallelepiped ceramic element assembly and a pair of external terminal electrodes formed on an outer surface of the ceramic element assembly. The external terminal electrodes are mostly formed in such a manner that a conductive paste is applied to end portions of the ceramic element assembly by an immersion method and is baked. In this way, each external terminal electrode is formed to extend over five surfaces in total with one end surface of the ceramic element assembly as a center.
In recent years, there has been an increase in demand for electronic components for specialized applications, and the like, in which the shape and arrangement of the external terminal electrodes of the ceramic electronic component have been progressively diversified with a diversification of the configurations in which electronic components are mounted. For example, Japanese Unexamined Patent Application Publication No. 2006-216622 and Japanese Unexamined Patent Application Publication No. 2006-339337 suggest a type of electric component in which external terminal electrodes are formed on one surface or two opposite surfaces of the ceramic element assembly.
When the external terminal electrodes are formed on one surface or two opposite surfaces of the ceramic element assembly, it is possible to form the external terminal electrodes by methods other than the immersion method. For example, a method may be employed that a conductive paste film for external terminal electrodes is printed on a principal surface of a collective component that constitutes a plurality of ceramic element assemblies for a plurality of ceramic electronic components and is baked, and then the collective component is divided to obtain the ceramic element assemblies for individual ceramic electronic components, which is, for example, described in Japanese Unexamined Patent Application Publication No. 9-260187 (particularly, at paragraph [0003]).
If a cutter, such as a dicer, is used to divide the collective component, there is a possibility that a crack or a chip may occur in the ceramic element assembly of each ceramic electronic component because the collective component to be divided is formed of sintered hard ceramics. To solve the above problem, Japanese Unexamined Patent Application Publication No. 9-260187 suggests that an unfired collective component is press-cut by a plate-like cutting blade. However, there is a problem in this method since the raw chips tend to stick one another after cutting.
Another method could be the break method that is often used in manufacturing a ceramic multilayer board, or the like. In the break method, a break groove is formed in an unfired collective component, and, after firing, a collective component is divided along the break grooves. There is no problem such as that occurs when a dicer or a plate-like cutting blade is used, as described above. In addition, it is excellent in production efficiency because a plating process or a measurement process may be performed in a state of a collective component.
Various break methods have been suggested. Among others, the break method described in Japanese Unexamined Patent Application Publication No. 2003-273272 is attractive. According to a technique described in Japanese Unexamined Patent Application Publication No. 2003-273272, by forming discontinuous linear break grooves, it is possible to prevent the occurrence of an undesirable crack in a collective component in handling the collective component for additional processes.
On the other hand, it has been suggested to bury a ceramic electronic component inside the multilayer wiring board in recent years, in order to miniaturize the multilayer wiring boards. For example, Japanese Unexamined Patent Application Publication No. 2005-064446 describes a method of manufacturing a laminating module. The method includes processes in which, when a ceramic electronic component is buried inside a board, the ceramic electronic component is accommodated in a core board so that an external terminal electrode formed on a principal surface of the ceramic electronic component is, for example, positioned to face upward, an insulating layer is formed so as to cover the core board and the ceramic electronic component, a laser beam is used to form a via hole that reaches the surface of the external terminal electrode, and then the via hole is filled with a conductor to electrically connect a wiring circuit with the external terminal electrode.
In the above burying, accurate laser beam irradiation is required. This is because there is a possibility that the characteristics of the ceramic electronic component are changed if the ceramic element assembly is erroneously irradiated with the laser beam.
Thus, the area of the external terminal electrode of the buried ceramic electronic component is desirably as large as possible. For example, in the monolithic ceramic electronic component of a type described in Japanese Unexamined Patent Application Publication No. 2006-216622 and Japanese Unexamined Patent Application Publication No. 2006-339337, as shown in FIG. 17, it is necessary to design external terminal electrodes 2 and 3 and increase the areas thereof as much as possible with leaving only a necessary gap 1.
However, when the break method of breaking along a predetermined break line in which break grooves like discontinuous perforations are formed is used to manufacture the ceramic electronic components in which a plurality of external terminal electrodes having narrow gaps between them are formed as described above, it is found that “break defects” tend to occur. A “break defect” is where a portion of a side surface of a ceramic element assembly formed during breaking along a gap portion is not broken properly, and, therefore, a protrusion (dent at the opposite side) is formed at the side surface, or a crack or a chip occurs in the ceramic element assembly starting from the gap portion.
As described in Japanese Unexamined Patent Application Publication No. 2003-273272, it is highly likely that no recess for leading a break is formed at a narrow gap portion and two adjacent recesses for leading a break are arranged with the gap portion placed in between when discontinuous equal-sized recesses for leading a break are formed at an equal pitch. In this case, it is easy to concentrate tensile stress between adjacent recesses for leading a break in external terminal electrode forming portions that occupy the majority of the principal surface, but it is difficult to concentrate tensile stress on a gap portion that has a narrow area and that is located at a level slightly lower than the external terminal electrode forming portion. For this reason, it is predictable that “break defect” tends to occur starting from the gap portion.